Shell-molds for investment casting may be made by applying a slurry containing a binder and a refractory powder to a wax or plastic pattern of the desired form. The slurry coats the wax, and excess slurry is allowed to drain off. A coarser refractory powder (the “stucco”) may be optionally applied onto the wet wax pattern, and this combination allowed to dry. Additional coatings of slurry and stucco may be applied until the mold has the required thickness and potential strength. The wax may then be removed. Molten metal may then be poured into the shell-mold and cooled to produce a metal casting.